Taittirīyopaniṣat 01.04

अथाधिलोकम्। पृथिवी पूर्वरूपम्। द्यौरुत्तररूपम्। आकाशः सन्धिः। वायुः सन्धानम्। इत्यधिलोकम् ॥४॥

athādhilokam। pṛthivī pūrvarūpam। dyauruttararūpam। ākāśaḥ sandhiḥ। vāyuḥ sandhānam। ityadhilokam ॥4॥

[अथ (atha) - now; then; अधिलोकम् (adhilokam) - with regard to the worlds; पृथिवी (pṛthivī) - earth; पूर्वरूपम् (pūrvarūpam) - former form; द्यौः (dyauḥ) - heaven; उत्तररूपम् (uttararūpam) - latter form; आकाशः (ākāśaḥ) - space; सन्धिः (sandhiḥ) - junction; वायुः (vāyuḥ) - air; सन्धानम् (sandhānam) - connection / bringing together; इति (iti) - thus; अधिलोकम् (adhilokam) - with regard to the worlds;]

Now, concerning the worlds: the earth is the prior form, heaven is the latter form, space is the junction, air brings them together; thus is the teaching regarding the worlds.